Conventional pyrolysis is a heated process in the range of 200-500° C. that converts biomass into pyrolysis liquid, char, and gas, usually in the absence of oxygen and focused on obtaining char in high yield. Fast pyrolysis, also referred to as flash pyrolysis, on the other hand is a process, in which biomass is quickly heated to a controlled pyrolysis temperature, and in which the gas phase is cooled quickly, whereby it partly condenses to pyrolysis liquid. This method generally obtains a higher yield of liquid and normally seeks to minimize the yield of the other two products. When the biomass decomposes at the elevated pyrolysis temperature, e.g. 450-600° C., three primary products are formed: gas, pyrolysis liquid and char.
Various methods and apparatus for producing gas or liquid from organic material have been proposed in the prior art. U.S. Pat. No. 5,413,227 discloses an ablative pyrolysis process in a vortex reactor system, and WO 03/057800 discloses an ablative thermolysis reactor including rotating surfaces. WO 92/09671 discloses a method and apparatus employing a vessel, which forms a torus or helix, through which feedstock can be conveyed at a velocity which sustains the feedstock against the outer periphery of the internal surface of the vessel as it transits the vessel. WO 01/34725 discloses an example of flash-pyrolysis in a cyclone. Further examples of pyrolysis apparatus are provided in WO 88/09364 and CA 2 365 785.
Though the prior art pyrolysis systems are useful for many purposes, they have been found to have certain limitations, as some of them are bulky, some have a low efficiency, and some require adjustment of e.g. rotor blades, which reduces overall cost efficiency. It has also been found that one barrier to efficient exploitation of biomass in fuel production is the cost conferred by collection and transportation of the biomass. Biomass is usually collected from growth sites, where it is loaded onto a truck or trailer for transportation thereof to a pyrolysis facility. Due to the relatively low concentration of energy per volume of biomass, production of even small amounts of usable pyrolysis liquid requires collection, transportation and storage of large volumes of biomass.